EP3013918B1 - Hydrophobic polyurethane adhesive - Google Patents

Description

The present invention relates to a polyurethane adhesive containing an isocyanate component A and a polyol component B, wherein the isocyanate component A is at least one diisocyanate or polyisocyanate and the polyol component B is the alkoxylation product of a mixture of castor oil or ricinoleic acid (i), an aromatic di- or polyol (ii) and one OH-functional compound with aliphatic OH groups and an OH functionality of 1 to 8 (iii) and optionally a compound (iv) selected from the group consisting of cyclic anhydrides of dicarboxylic acids and optionally a compound (v) from the group consisting of cyclic mono- or diesters. The present invention further relates to a method for bonding using the polyurethane adhesive according to the invention, an article bonded using the polyurethane adhesive and the use of this article in the construction of wind power plants.

Polyurethane adhesives based on an isocyanate component and a polyol component, so-called two-component polyurethane adhesives, are known and are used, for example, in the bonding of plastics. Particularly when these polyurethane adhesives are used as structural adhesives, i.e. when load-bearing structures are to be glued, high demands are placed on the strength and adhesive strength. High strengths are obtained via high crosslinking densities, which are usually achieved by using more functional isocyanates and compounds that are reactive toward isocyanates.

Such supporting structures are e.g. the bonding of fiber-reinforced components for wings or other components of airplanes, of fiber-reinforced components of boats and in particular of fiber-reinforced components for the production of blades for wind turbines.

So after WO 2006/084900 A2 a two-component polyurethane composition is known in which a mixture of at least one alkoxylated aromatic diol and at least one aliphatic triol and a polyisocyanate component containing at least one polyisocyanate is used.

In particular in the production of large-area sandwich structures, such as, for example, in the production of wind blades for wind power plants, it is necessary that the adhesives can be processed for a long time after the polyol and isocyanate components have been mixed. In order to avoid side reactions of the isocyanate, for example with atmospheric moisture, which leads to a shortening of the open time and a deterioration in the mechanical properties of the cured adhesive, the adhesives are adjusted by the use of hydrophobic components so that no water from the air is absorbed by the adhesive composition and suppress such side reactions.

So revealed WO 2009080740 a two-component polyurethane adhesive which consists of an isocyanate component and a polyol component, the polyol component containing a high molecular weight polyester diol, a highly functional polyol and hydrophobic polyols, preferably selected from polycarbonate polyols, polybutadiene polyols or oleochemical polyols, such as in particular castor oil.

Disadvantages are the inadequate adhesive strength despite the hydrophobicity and the reduced chemical resistance due to the use of polyester diol, particularly in the alkaline range. Furthermore, the solution is on WO 2009/080740 A1 disadvantageous that, due to the proposed composition, the high strengths and high moduli of elasticity required for numerous bonds cannot be achieved.

EP 2468789 discloses a two-component polyurethane adhesive, the polyol component comprising castor oil, at least one aromatic diol and at least one polyol having 5 to 8 hydroxyl groups.

These adhesives are in need of improvement with regard to their mechanical properties. In particular tensile strength, elongation at break and modulus of elasticity as well as tensile shear strength are essential properties in the production of structural bonds. In addition, in particular in the structural bonding of blades for wind turbines, it is necessary for the adhesive to have a high softening temperature, since the structural bonds are exposed to elevated temperatures, for example due to solar radiation. In addition to solar radiation, the mechanical stress on the components also causes a not inconsiderable amount of heat. For example, Germanischer Lloyd demands structural heat resistance of at least 65 ° C for structural adhesives in the construction of wind turbines.

Another disadvantage of the adhesives from the prior art is a certain spread of the mechanical properties depending on the batch obtained. This is due to minor changes in the composition of the natural product castor oil.

It was therefore an object of the present invention to provide a polyurethane adhesive which, when cured, has very good mechanical properties, in particular tensile strength, elongation at break, modulus of elasticity and tensile shear strength, and leads to bonds which are as uniform as possible, regardless of the product batch produced. Another object of the present invention was to provide a polyurethane adhesive which, in addition to the outstanding mechanical properties in the hardened state, has a glass transition temperature of more than 60 ° C.

This object is achieved by a polyurethane adhesive comprising an isocyanate component A and a polyol component B, the isocyanate component A being at least one diisocyanate or polyisocyanate and the polyol component B being the alkoxylation product Mixture of castor oil or ricinoleic acid (i), an aromatic di- or polyol (ii) and an OH-functional compound with aliphatically bound OH groups and an OH functionality of 1 to 8 polyol (iii) and optionally a compound (iv) , selected from the group consisting of cyclic anhydrides of dicarboxylic acids and optionally a compound (v) selected from the group consisting of cyclic mono- or diesters.

The polyisocyanate component A contains at least one diisocyanate or polyisocyanate. These include all aliphatic, cycloaliphatic and aromatic di- or polyvalent isocyanates known for the production of polyurethanes, as well as any mixtures thereof. Examples are 4,4'-methane diphenyl diisocyanate, 2,4'-methane diphenyl diisocyanate, the mixtures of monomeric methane diphenyl diisocyanates and higher-core homologues of methane diphenyl diisocyanate (polymer-MDI), tetramethylene diisocyanate, hexamethylene diisocyanate (HDI), the mixtures of hexamethylene diisocyanates and higher-core homologues -HDI), isophorone diisocyanate (IPDI), 2,4- or 2,6-tolylene diisocyanate (TDI) or mixtures of the isocyanates mentioned. Toluene diisocyanate (TDI), diphenylmethane diisocyanate (MDI) and in particular mixtures of diphenylmethane diisocyanate and polyphenylene polymethylene polyisocyanates are preferably used. The isocyanates can also be modified, for example by incorporating uretdione, carbamate, isocyanurate, carbodiimide, allophanate and in particular urethane groups.

Isocyanate prepolymers containing isocyanate groups can also be used as di- and polyisocyanates. These polyisocyanate prepolymers can be obtained by reacting the di- and polyisocyanates described above, for example at temperatures from 30 to 100 ° C., preferably at about 80 ° C., with polyols to form the prepolymer. 4,4'-MDI is preferably used together with uretonimine-modified MDI and commercially available polyols based on polyesters, for example starting from adipic acid, or polyethers, for example starting from ethylene oxide and / or propylene oxide, for the preparation of the prepolymers according to the invention.

Polyols which can be used to prepare isocyanate prepolymers are known to the person skilled in the art and are described, for example, in " Plastics Handbook, Volume 7, Polyurethane ", Carl Hanser Verlag, 3rd edition 1993, Chapter 3.1 , Polyols, which are also described under polyol component B, are preferably used as polyols for the production of isocyanate prepolymers. In particular, no polyisocyanate prepolymers are used in polyisocyanate component A.

Mixtures of diphenylmethane diisocyanate and polyphenylene polymethylene polyisocyanates are particularly preferably used as the di and polyisocyanates.

The polyol component contains the alkoxylation product of a mixture of castor oil or ricinoleic acid (i), an aromatic di- or polyol (ii) and an OH-functional compound with aliphatically bound OH groups and an OH functionality of 1 to 8 (iii) and optionally a compound (iv) selected from the group consisting of cyclic anhydrides of dicarboxylic acids and optionally a compound (v) selected from the group, consisting of cyclic mono- or diesters.

The alkoxylation is preferably carried out in that the mixture of castor oil or ricinoleic acid (i), an aromatic di- or polyol (ii) and an OH-functional compound with aliphatically bound OH groups and an OH functionality of 1 to 8 (iii) and optionally a compound (iv) selected from the group consisting of cyclic anhydrides of dicarboxylic acids and optionally a compound (v) selected from the group consisting of cyclic mono- or diesters with the aid of a nucleophilic and / or basic catalyst and at least one alkylene. The mixture of components (i) to (iii) and optionally (iv) and (v) is preferably initially introduced into a reaction vessel before the alkylene oxide is added. For example, 1,2-butylene oxide, propylene oxide or ethylene oxide can be used as the alkylene oxide. The alkylene oxide preferably contains propylene oxide, particularly preferably the alkylene oxide consists of propylene oxide.

The basic and / or nucleophilic catalyst can be selected from the group consisting of alkali metal or alkaline earth metal hydroxides, alkali metal or alkaline earth metal alkoxides, tertiary amines, N-heterocyclic carbenes or precursors of N-heterocyclic carbenes.

The basic and / or nucleophilic catalyst is preferably selected from the group comprising tertiary amines.

The basic and / or nucleophilic catalyst is particularly preferably selected from the group comprising imidazole and imidazole derivatives, very particularly preferably imidazole.

In another preferred embodiment, the basic and / or nucleophilic catalyst is selected from the group containing N-heterocyclic carbenes, particularly preferably from the group containing N-heterocyclic carbenes based on N-alkyl- and N-aryl-substituted imidazolylidenes.

In a preferred embodiment, the basic and / or nucleophilic catalyst is selected from the group comprising trimethylamine, triethylamine, tripropylamine, tributylamine, N, N'-dimethylethanolamine, N, N'-dimethylcyclohexylamine, dimethylethylamine, dimethylbutylamine, N, N'-dimethylaniline, 4-dimethylaminopyridine, N, N'-dimethylbenzylamine, pyridine, imidazole, N-methylimidazole, 2-methylimidazole, 1,2 dimethylimidazole, N- (3-aminopropyl) imidazole), 4-methylimidazole, 5-methylimidazole, 2-ethyl- 4-methylimidazole, 2,4-dimethylimidazole, 1-hydroxypropylimidazole, 2,4,5-trimethylimidazole, 2-ethylimidazole, 2-ethyl-4-methylimidazole, N-phenylimidazole, 2-phenylimidazole, 4-phenylimidazole, guanidine, alkylated guanidines , 1,1,3,3-tetramethylguanidine, piperazine, alkylated piperazines, piperidine, alkylated pipiridine, 7-methyl-1,5,7-triazabicyclo [4.4.0] dec-5-ene, 1,5-diazobicylco [4.3.0] -non-5-ene, 1,5-diazabicylo [5.4.0] undec-7-ene, preferably imidazole and dimethylethanolamine (DMEOA).

The catalysts mentioned can be used alone or in any mixtures with one another.

The reaction with alkylene oxide usually takes place at temperatures in the range between 80 and 200 ° C., preferably between 100 ° C. and 160 ° C., particularly preferably between 110 ° C. and 150 ° C.

If tertiary amines and / or N-heterocyclic carbenes are used as catalysts for the reaction with alkylene oxides, the catalyst concentration is based on the mass of the compounds (i) to (iii) and, if present (iv) and (v), between 50- 5000 ppm, preferably between 100 and 1000 ppm, and the catalyst does not have to be removed from the reaction product after the reaction.

Castor oil (i) is a renewable raw material and is obtained from the seeds of the castor bean. Castor oil is essentially a triglyceride of a fatty acid mixture containing, based on the total weight of the fatty acid mixture> 75% by weight of ricinoleic acid, 3 to 10% by weight of oleic acid, 2 to 6% by weight of linoleic acid, 1 to 4% by weight Stearic acid, 0 to 2% by weight of palmitic acid and optionally small amounts of less than 1% by weight of further fatty acids such as linolenic acid, vaccenic acid, archic acid and eicosenoic acid. Alternatively, part of castor oil can also be replaced by ricinoleic acid. The proportion of ricinoleic acid is preferably not more than 40% by weight, particularly preferably 20% by weight, more preferably 10% by weight and in particular 5% by weight, in each case based on the total weight of component (i). The proportion of component (i) in the total weight of the mixture to be alkoxylated is preferably 30 to 90% by weight, particularly preferably 40 to 85% by weight and in particular 45 to 80% by weight, in each case based on the total weight of the components (i) to (iii) and (if present) (iv) and (v).

In addition to castor oil and ricinoleic acid (i), the mixture to be alkoxylated can contain further triglycerides of fatty acids, such as trans-oil, tallow, soybean oil, rapeseed oil, olive oil, sunflower oil, hydroxyl-modified soybean oil, palm oil, and derivatized castor oil, and fatty acids or mixtures of these substances derived from these triglycerides contain.

Oils modified with hydroxyl groups can also be added to the mixture to be alkoxylated. The oils, that is to say the fatty acid triglycerides or the fatty acids, can be modified via the generally known methods, for example via hydroformylation / hydrogenation or epoxidation / ring opening, ozonolysis, direct oxidation or nitrous oxide oxidation / reduction.

The proportion of castor oil and ricinoleic acid (i) in the total weight of the triglycerides and fatty acids contained in the mixture to be alkoxylated is preferably at least 50% by weight, particularly preferably at least 70% by weight and in particular at least 80% by weight.

A compound which contains at least two aromatically bound hydroxyl groups is used as the aromatic diol or polyol (ii). Alternatively, a di- or polyol obtained by alkoxylation of an aromatic di- or polyol can also be used as the aromatic di- or polyol, this being less preferred. If an alkoxylation product of an aromatic polyol is used as component (ii), the hydroxyl number of the aromatic diol or polyol must be greater than 350 mg KOH / g, preferably greater than 400 mg KOH / g and particularly preferably greater than 450 mg KOH / g. The aromatic diol preferably contains at least two phenol groups, particularly preferably the aromatic diol (ii) contains a bisphenol, more preferably the aromatic diol or polyol is a bisphenol.

Bisphenols are compounds with two hydroxyphenyl groups. These include bisphenol A (2,2-bis (4-hydroxyphenyl) propane); Bisphenol AF (1,1-bis (4-hydroxyphenyl) -1-phenylethane), bisphenol AP (1,1-bis (4-hydroxyphenyl) -1-phenylethane), bisphenol B (2,2-bis (4-hydroxyphenyl ) butane), bisphenol BP (bis- (4-hydroxyphenyl) diphenylmethane), bisphenol C (2,2-bis (3-methyl-4-hydroxyphenyl) propane), bisphenol E (1,1-bis (4-hydroxyphenyl) ethane), bisphenol F (bis (4-hydroxyphenyl) methane), bisphenol FL (9,9-bis (4-hydroxyphenyl) fluorene), bisphenol G (2,2-bis (4-hydroxy-3-isopropylphenyl)) propane), bisphenol M (1,3-bis (2- (4-hydroxyphenyl) -2-propyl) benzene), bisphenol P (1,4-bis (2- (4-hydroxyphenyl) -2-propyl) benzene) , Bisphenol PH (2,2- [5,5'-bis [1,1 '- (biphenyl) -2-ol]] propane), bisphenol S (bis (4-hydroxyphenyl) sulfone), bisphenol TMC (1, 1-bis (4-hydroyphenyl) -3,3,5-trimethyl-cyclohexane) or bisphenol Z (1,1-bis (4-hydroxyphenyl) cyclohexane), bisphenol A and bisphenol S, in particular bisphenol A, are particularly preferred.

In a particularly preferred embodiment, the aromatic di- or polyol (ii) is bisphenol A or bisphenol S, in particular bisphenol A. The proportion of component (ii) in the total weight of the mixture to be alkoxylated is preferably 4 to 30% by weight, particularly preferably 5 to 25% by weight, based in each case on the total weight of components (i) to (iii) and, if present, (iv) and (v).

As an aliphatic of an OH-functional compound with aliphatically bound OH groups and an OH functionality of 1 to 8 (iii), compounds are suitable which have one to 8 aliphatically bound hydroxyl groups, compounds which are defined as component (ii ) fall, should not be understood as compounds of component (iii). Examples are water, propylene glycol, ethylene glycol, diethylene glycol, dipropylene glycol, neopentyl glycol, 1,2-butanediol, 1,3-butanediol, 1,4-butanediol, hexanediol, pentanediol, 3-methyl-1,5-pentanediol, 1,12- Dodecanediol, monofunctional alcohols, such as ethanol and propanol, glycerol, trimethylolpropane, pentaerythritol, 1,2,4- or 1,3,5-trihydroxycyclohexane, sorbitol and Sucrose and reaction products of such compounds with alkylene oxides such as propylene oxide or ethylene oxide and mixtures thereof. Component (iii) may also contain esters and / or polyesters containing OH groups. Esters and polyesters are preferably obtained from organic dicarboxylic acids having 2 to 12 carbon atoms, preferably aliphatic dicarboxylic acids having 4 to 6 carbon atoms and polyhydric alcohols, preferably diols, having 2 to 12 carbon atoms, preferably 2 to 6 carbon atoms. Examples of suitable dicarboxylic acids are: succinic acid, glutaric acid, adipic acid, suberic acid, azelaic acid, sebacic acid, decanedicarboxylic acid, maleic acid, fumaric acid, phthalic acid, isophthalic acid and terephthalic acid. The dicarboxylic acids can be used both individually and in a mixture with one another. Instead of the free dicarboxylic acids, the corresponding dicarboxylic acid derivatives, such as, for example, dicarboxylic acid esters of alcohols having 1 to 4 carbon atoms or dicarboxylic acid anhydrides, can also be used. Dicarboxylic acid mixtures of succinic, glutaric and adipic acid and in particular adipic acid are preferably used. Examples of two and polyhydric alcohols, in particular diols, are ethanediol, diethylene glycol, 1,2- or 1,3-propanediol, dipropylene glycol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,10- Decanediol, glycerin and trimethylolpropane. Ethanediol, diethylene glycol, 1,4-butanediol, 1,5-pentanediol and 1,6-hexanediol are preferably used. Polyester polyols from lactones, for example ε-caprolactone or hydroxycarboxylic acids, for example ω-hydroxycaproic acid, can also be used. The ester or polyester is prepared in a known manner.

Component (iii) preferably has an OH number of at least 50, particularly preferably at least 200 and in particular at least 600 mg KOH / g. Compounds which are used as aliphatic polyol (iii) particularly preferably have 5 to 8 OH groups. A particularly preferred example of a compound of component (iii) is a sugar, in particular sucrose or sorbitol, particularly preferably sucrose.

The proportion of component (iii) in the total weight of the mixture to be alkoxylated is preferably 2 to 40% by weight, particularly preferably 3 to 25% by weight and in particular 4 to 20% by weight, in each case based on the total weight of the components (i) to (iii) and (if present) (iv) and (v).

A compound selected from the group consisting of cyclic anhydrides of dicarboxylic acids is used as the compound (iv), which can optionally be used. The anhydrides of dicarboxylic acid are preferably selected from the group comprising a) alkenylsuccinic anhydrides, b) phthalic anhydride, c) maleic anhydride, d) succinic anhydride and e) tetrahydrophthalic anhydride and mixtures thereof.

The alkenylsuccinic anhydrides a) are preferably selected from the group of the C12-C20-alkyl chain-substituted succinic anhydrides and the poly (isobutylene) succinic anhydrides with a molecular weight between 500 and 2000 g / mol. The at least one alkenyl succinic anhydride a) is in one embodiment of the process according to the invention preferably selected from the group containing C18 and / or C16 alkenyl succinic anhydrides, poly (isobutylene) succinic anhydride and mixtures thereof.

The proportion of component (iv) in the total weight of the mixture to be alkoxylated is preferably 0 to 30% by weight, particularly preferably 2 to 25% by weight and in particular 4 to 20% by weight, in each case based on the total weight of the components (i) to (iii) and (if present) (iv) and (v).

A compound selected from the group consisting of selected from the group consisting of cyclic mono- or diesters is used as the compound (v), which can optionally be used. Compound (v) is preferably selected from the group comprising γ-butyrolactone, δ-valerolactone, ε-caprolactone, (R, R) lactide, (S, S) lactide, meso-lactide, and mixtures thereof; ε-caprolactone is particularly preferred as compound (v).

The proportion of component (v) in the total weight of the mixture to be alkoxylated is preferably 0 to 30% by weight, particularly preferably 2 to 25% by weight and in particular 4 to 20% by weight, in each case based on the total weight of the components (i) to (iii) and (if present) (iv) and (v).

The alkoxylation of the mixture of components (i) to (iii) and, if present (iv) and (v) with the corresponding amount of alkylene oxide, is usually carried out until an OH number of 80 to 800 mg KOH / g, preferably 150 to 600 mg KOH / g and particularly preferably 200 to 500 mg KOH / g is set.

In addition to the alkoxylation product of components (i) to (iii) and, if present (iv) and (v), it is also possible to use further compounds which are customary in polyurethane chemistry and have isocyanate-reactive groups, such as polyols and chain extenders and crosslinking agents. Such are described for example in " Plastics Handbook, Volume 7, Polyurethane ", Carl Hanser Verlag, 3rd edition 1993, chapters 3.1 and 3.4.3 , and especially for polyurethane adhesive applications in " The Polyurethanes Book ", Wiley, 2002, chapters 23 and 25 , These preferably contain exclusively OH groups as isocyanate-reactive groups and are preferably used in amounts of less than 90% by weight, particularly preferably less than 50% by weight, more preferably less than 30% by weight, more preferably less than 10% by weight. -% and in particular less than 1 wt .-%, based on the total weight of all compounds with isocyanate-reactive groups in the polyol component B.

The polyurethane adhesives according to the invention can also contain further additives customary in the production, such as solvents, plasticizers, fillers, such as carbon blacks, chalks and talc, adhesion promoters, in particular silicon compounds, such as trialkoxysilanes, thixothropierizing agents, such as amorphous silicas and drying agents, such as zeolites. These additives are usually added to the polyol component of polyol component B.

The present invention furthermore relates to a method for bonding, in which the isocyanate component A and the polyol component B of a polyurethane adhesive according to the invention are mixed, the mixed polyurethane adhesive is applied to at least one substrate surface to be bonded, the substrate surfaces are joined within the open time and the polyurethane adhesive is allowed to harden. The mixing is preferably carried out at an isocyanate index of 80 to 200, particularly preferably 90 to 150, more preferably 95 to 120 and in particular 98 to 110. In the context of the present invention, the isocyanate index is the stoichiometric ratio of isocyanate groups to isocyanate-reactive Groups multiplied by 100 understood.

An adhesive according to the invention preferably has a long open time of at least 30 minutes at room temperature. The open time is the period from mixing the polyisocyanate component A and the polyol component B and subsequent application of the adhesive, the joining of the adhesive parts is still possible before the adhesive has hardened to such an extent that it is no longer able to form an adhesive connection.

The polyurethane adhesive according to the invention can be used as a structural adhesive, in particular for bonding plastic parts, preferably fiber-reinforced plastic parts. Applications are, for example, in vehicle construction, in the construction of aircraft, in particular the wings of aircraft or wind turbines, in particular rotor blades for wind turbines, and are distinguished by excellent mechanical properties and a high glass transition temperature with a long open time.

An advantage of the process according to the invention is that the alkoxylation product of components (i) to (v) can be used to convert those compounds into a homogeneous reaction product which are distinguished by a very large difference in polarity and are therefore incompatible with one another in pure form. The reaction with alkylene oxide makes the mutually incompatible molecules compatible and results in homogeneous reaction products which contain both polyether units and polyester units. In the case of base-catalyzed alkoxylation, this is probably also due to the fact that in the process, in addition to the ring-opening polymerization, transesterification reactions take place at the same time, which ensures the homogeneous distribution of the ester-carrying molecular chains with the ether-carrying molecular chains. In this way, polyurethane adhesives with excellent properties are obtained, both during processing and after excellent mechanical properties of the adhesive itself.

The invention is illustrated below with the aid of examples.

• Polyol1: Sovermol® 805, ein Gemisch aus Rizinusöl und einem Ketonharz in ein Mischverhältnis von etwa 80/20 Gewichtsteilen, mit einer OH Zahl von 173 mg KOH/g, kommerziell erhältlich von der BASF SE
• Polyol 2: Ein Sucrose/Glyzerin haltiges Propoxylat mit einer OH Zahl von 490 mg KOH/g und eine mitteleren Funktionolität von 4,3
• Polyol 3: Propoxylat, ausgehend von Bisphenol A als Starter mit einer OH Zahl von 280 mg KOH/g.
• Iso 1: Polymer-MDI mit einer Funktionalität von ca. 2,7 und einem NCO-Gehalt von 31,5 Gew.-%, erhältlich unter dem HandelsnamenLupranat® M20 von der BASF SE.
• Wasserfänger: Zeolitischer Wasserfänger, dispergiert in Ricinusöl (50 Gew.-%)

Raw materials used:

• Polyol1: Sovermol® 805, a mixture of castor oil and a ketone resin in a mixing ratio of about 80/20 parts by weight, with an OH number of 173 mg KOH / g, commercially available from BASF SE
• Polyol 2: A sucrose / glycerol-containing propoxylate with an OH number of 490 mg KOH / g and an average functionality of 4.3
• Polyol 3: propoxylate, starting from bisphenol A as a starter with an OH number of 280 mg KOH / g.
• Iso 1: polymer MDI with a functionality of approx. 2.7 and an NCO content of 31.5% by weight, available under the trade name Lupranat® M20 from BASF SE.
• Water scavenger: Zeolitic water scavenger, dispersed in castor oil (50% by weight)

Polyolsynthesebeispiele Polyol Synthesis Example 1 (Synthesis 1):

175.2 g glycerol, 0.5 g imidazole, 275.45 g sorbitol and 425.1 g bisphenol A and 2751.7 g castor oil (FSG quality) were placed in a 5 L reactor at 25 ° C. This was then rendered inert with nitrogen. The kettle was heated to 150 ° C. and 1372.1 g of propylene oxide were metered in. After a reaction time of 11 h, the mixture was evacuated at 100 ° C. under full vacuum for 40 minutes and then cooled to 25 ° C. 4933 g of product were obtained.

• OH-Zahl: 300,2 mg KOH/g
• Viskosität (25 °C): 2021 mPas
• Säurezahl: kleiner 0,01 mg KOH/g
• Wassergehalt: 0,02 Gew.-%
• Restgehalt Bisphenol A: kleiner 10 mg/kg per HPLC bestimmt

The polyether ester obtained had the following characteristics:

• OH number: 300.2 mg KOH / g
• Viscosity (25 ° C): 2021 mPas
• Acid number: less than 0.01 mg KOH / g
• Water content: 0.02% by weight
• Residual bisphenol A: less than 10 mg / kg determined by HPLC

Polyol Synthesis Example 2 (Synthesis 2):

5.7 g glycerol, 0.02 g imidazole, 14.5 g sorbitol and 30.2 g bisphenol A and 122.4 g castor oil (FSG quality) were placed in a 300 mL reactor at 25 ° C. This was then rendered inert with nitrogen. The kettle was heated to 150 ° C. and 67.2 g of propylene oxide were metered in. After a reaction time of 19 h, the mixture was evacuated at 100 ° C. under full vacuum for 40 minutes and then cooled to 25 ° C. 225.9 g of product were obtained.

• OH-Zahl: 314,7 mg KOH/g
• Mittlere OH-Funktionalität 3,2
• Viskosität (25 °C): 3170 mPas
• Säurezahl: kleiner 0,01 mg KOH/g
• Wassergehalt: kleiner 0,04%
• Restgehalt Bisphenol A: kleiner 10 mg/kg per HPLC bestimmt

The polyether ester obtained had the following characteristics:

• OH number: 314.7 mg KOH / g
• Average OH functionality 3.2
• Viscosity (25 ° C): 3170 mPas
• Acid number: less than 0.01 mg KOH / g
• Water content: less than 0.04%
• Residual bisphenol A: less than 10 mg / kg determined by HPLC

Polyol Synthesis Example 3 (Synthesis 3):

3.4 g glycerol, 0.02 g imidazole, 22.3 g sucrose as well as 36.0 g bisphenol A and 112.4 g castor oil (FSG quality) were placed in a 300 mL reactor at 25 ° C. This was then rendered inert with nitrogen. The kettle was heated to 130 ° C. and 65.9 g of propylene oxide were metered in. After a reaction time of 10 h, the mixture was evacuated at 100 ° C. under full vacuum for 40 minutes and then cooled to 25 ° C. 229.0 g of product were obtained.

• OH-Zahl: 310,6 mg KOH/g
• Mittlere OH-Funktionalität 3,4
• Viskosität (25 °C): 7786 mPas
• Säurezahl: kleiner 0,01 mg KOH/g
• Wassergehalt: kleiner 0,04%
• Restgehalt Bisphenol A: kleiner 10 mg/kg per HPLC bestimmt??

The polyether ester obtained had the following characteristics:

• OH number: 310.6 mg KOH / g
• Average OH functionality 3.4
• Viscosity (25 ° C): 7786 mPas
• Acid number: less than 0.01 mg KOH / g
• Water content: less than 0.04%
• Residual bisphenol A: less than 10 mg / kg determined by HPLC ??

Polyol synthesis example 4 (synthesis 4; comparative example without bisphenol-A):

210.0 g glycerol, 0.5 g imidazole, 335.0 g sorbitol and 2749.7 g castor oil (FSG quality) were placed in a 5000 mL reactor at 25 ° C. This was then rendered inert with nitrogen. The kettle was heated to 150 ° C. and 1704.8 g of propylene oxide were metered in. After a reaction time of 4 h, the mixture was evacuated at 100 ° C. under full vacuum for 60 minutes and then cooled to 25 ° C. 4982.5 g of product were obtained.

• OH-Zahl: 308,9 mg KOH/g
• Viskosität (25 °C): 1287 mPas
• Säurezahl: kleiner 0,01 mg KOH/g
• Wassergehalt: kleiner 0,01%

The polyether ester obtained had the following characteristics:

• OH number: 308.9 mg KOH / g
• Viscosity (25 ° C): 1287 mPas
• Acid number: less than 0.01 mg KOH / g
• Water content: less than 0.01%

Gluing and making a plate from the same reaction mixture: bonding:

The samples for determining the tensile shear strength (shear strength 0.5 mm) were produced in accordance with DIN EN 1465 "Determination of the tensile shear strength of high-strength overlap bonds". For this purpose, the starting materials according to Table 1 with an isocyanate index from 105 a speed mixer 90 seconds at 1600 rpm, then 30 seconds at 2100 rpm. The adhesive was then applied to a glass fiber reinforced epoxy plate (Vetronit® EGS 619, 100x25x2mm, Rocholl GmbH). The plate with the applied adhesive was then stored in a climatic cabinet at 25 ° C. and 70% atmospheric humidity for 60 min. A second plate was placed on the plate pretreated in this way. The adhesive layer thickness is 0.5 mm. The adhesive is loaded with a weight of 1 kg until the adhesive has hardened almost completely. The remaining adhesive is then removed and the bonded plates are cured again at 80 ° C. for 2 hours. The tension shear bodies are cut and tested in accordance with the DIN EN 1465 standard.

Mechanics plates 2 mm and 4 mm

An open mold with the desired depth (2mm or 4mm) is heated in a drying cabinet heated to 80 ° C for approx. 45min. The evacuated components are weighed into a speed mixer beaker and mixed in the speed mixer for 60s at 1600rpm, then 120s at 2100rpm. After the stirring process has ended, the reaction mixture is poured into the mold and smoothed out using a doctor blade. The plate is cured for 2 hours at 80 ° C. The test specimens are then punched out of the plates produced in this way. The mechanical parameters are determined in accordance with DIN EN ISO 527 on 2 mm thick test specimens, and the glass transition temperature is determined using dynamic differential thermal analysis (DSC) at a heating rate of 20 K / min in accordance with DIN EN ISO 11357.

Determining the open time:

The open time is determined via a reaction viscosity measurement in a plate-plate geometry rheometer with a diameter of 20 mm and a gap width of 1 mm. To produce the reaction mixture to be measured, the starting components according to Table 1 are stirred in a speed mixer at an isocyanate index of 105 5s at 1600 rpm. Immediately afterwards, enough adhesive is placed on the measuring plate so that the geometry is completely filled. Before the measurement is carried out for 10 seconds with a maximum shear rate of 100 s ^-1 . Pre-cut and in the subsequent pause of 120 seconds, excess material is removed. In the actual measurement, the time until a viscosity of 400 Pas is reached is determined as the open time at a shear rate of 1 s-1.

Table 1 shows that the use of polyols according to the invention gives adhesives with excellent properties, in particular a glass transition temperature of greater than 60 ° C., a shear strength of more than 10 N / mm ² and a high tensile strength of more than 35 MPa. The open time of adhesives according to the invention is greater than 60 minutes and therefore also allows the bonding of large-area structures, such as, for example, wind blades of wind power plants. In contrast, the use of finished polyols based on bisphenol A, a 5-functional starter and castor oil, such as in EP 2468789 described, either to low glass transition temperatures (comparison 4) or to low shear strengths (comparison 3). The omission of bisphenol A in the synthesis polyol (comparison 1) or the separate addition of bisphenol A polyol to a synthesis polyol without bisphenol A (comparison 2) also leads to adhesives with insufficient shear strengths.

Claims (13)

1. A polyurethane adhesive comprising an isocyanate component A and a polyol component B where the isocyanate component A comprises at least one diisocyanate or polyisocyanate and the polyol component B comprises the alkoxylation product of a mixture of castor oil or ricinoleic acid (i), of an aromatic di- or polyol (ii), and of an OH-functional compound having aliphatically bonded OH groups and OH-functionality of from 1 to 8 (iii), and also optionally of a compound (iv), selected from the group consisting of cyclic anhydrides of dicarboxylic acids, and optionally of a compound (v) selected from the group consisting of cyclic mono- or diesters.
2. The polyurethane adhesive according to claim 1, wherein the alkoxylation of the mixture of castor oil or ricinoleic acid (i), of an aromatic di- or polyol (ii), and of an OH-functional compound having aliphatically bonded OH groups and OH-functionality of from 1 to 8 (iii), and also optionally of a compound (iv), selected from the group consisting of cyclic anhydrides of dicarboxylic acids, and optionally of a compound (v) selected from the group consisting of cyclic mono- or diesters is achieved with the aid of a nucleophilic and/or basic catalyst and of at least one alkylene oxide.
3. The polyurethane adhesive according to claim 1 or 2, wherein the alkylene oxide comprises propylene oxide.
4. The polyurethane adhesive according to any of claims 1 to 3, wherein the aromatic diol comprises two phenol groups.
5. The polyurethane adhesive according to claim 4, wherein the aromatic diol comprises at least one bisphenol.
6. The polyurethane adhesive according to any of claims 1 to 5, wherein the OH-functional compound (iii) has from 5 to 8 OH groups.
7. The polyurethane adhesive according to any of claims 1 to 6, wherein the isocyanate component A comprises a mixture of monomeric diphenylmethane diisocyanate and of diphenylmethane diisocyanate having a larger number of rings.
8. The polyurethane adhesive according to any of claims 1 to 7, wherein the OH number of the alkoxylation product of a mixture of castor oil or ricinoleic acid (preferably castor oil) (i), of an aromatic di- or polyol (ii), and of an OH-functional compound having aliphatically bonded OH groups and OH-functionality of from 1 to 8 (iii), and also optionally of a compound (iv), selected from the group consisting of cyclic anhydrides of dicarboxylic acids, and optionally of a compound (v) selected from the group consisting of cyclic mono- or diesters is in the range from 80 to 800.
9. The polyurethane adhesive according to any of claims 1 to 8, wherein the proportion of castor oil or ricinoleic acid (preferably castor oil) (i) is from 30 to 80% by weight, the proportion of an aromatic di- or polyol (ii) is from 4 to 25% by weight, and the proportion of an OH-functional compound having aliphatically bonded OH groups and OH-functionality of from 1 to 8 (iii) is from 10 to 40% by weight, and the proportion of an optional compound (iv) selected from the group consisting of cyclic anhydrides of dicarboxylic acids is from 0 to 30% by weight, and the proportion of an optional compound (v) selected from the group consisting of cyclic mono- or diesters is from 0 to 30% by weight, based in each case on the total weight of components (i) to (v).
10. A process for adhesive bonding comprising the following steps:

    - mixing of the isocyanate component A and of the polyol component B of a polyurethane adhesive according to any of claims 1 to 9,

    - application of the mixed polyurethane adhesive to at least one substrate surface requiring adhesive bonding,

    - formation of a joint within the open time, and

    - hardening of the polyurethane adhesive.
11. The process according to claim 10, wherein the at least one substrate surface requiring adhesive bonding is a plastic.
12. An adhesive-bonded item obtainable by a process according to claim 10 or 11.
13. The use of an adhesive-bonded item according to claim 12 for the construction of wind turbines.